A known method of breaking or fracturing an optical fiber in a controlled manner is to weaken the fiber at the desired break location and then stress the fiber in tension so that a crack travels from the weakened zone across the axis of the fiber. U.S. Pat. No. 4,027,814 describes a particular method and apparatus in which the fiber is flexed very slightly when it is broken and the speed of propagation of the crack is controlled in a manner which produces a smooth fractured surface. The achievement of a smooth surface is desirable for the reason that such a surface can be placed against a similar surface on another fiber to form a splice and it is not necessary to polish the surfaces when an optical splice is made.
While it is important to have an optically smooth surface in a splice of fiber optic members, it is also important that the opposed surfaces of the optical fibers be parallel to each other or nearly so. Parallelism or substantial parallelism in the surfaces of the fibers in a splice is desirable for the reason that any departure from substantial parallelism results in serious losses in the splice.
The known methods of fracturing or breaking optical fibers do not produce fractured surfaces which are satisfactory from the standpoint of the fracture angle of the surface (the fracture angle being the departure of the surface from a surface which would extend normally of the fiber axis). The present invention is directed to the achievement of a method and apparatus for breaking optical fibers which will result in improvements in the quality of the fracture as related to the fracture angle. The invention is furthered directed to the achievement of a method and apparatus for breaking optical fibers which will produce a satisfactory surface insofar as smoothness is concerned.
A preferred embodiment of the invention comprises a method of breaking an optical fiber in which the fiber is weakened at the desired break location and the fiber is then stressed to cause the fiber to break at the desired break location. The method is characterized in that elastomeric material is placed in surrounding relationship to a portion of the fiber extending from the desired break location in opposite directions along the axis of the fiber so that the elastomeric material has ends which are spaced from the desired break location. The elastomeric material is compressed radially towards the axis of the fiber so that the interface surfaces of the fiber and the elastomeric material are pressed against each other to the extent that relative movement of the fiber and the elastic material is prevented and the elastomeric material is elongated as a result of the compression. As a result, the fiber is placed in tension causing the fiber to break by propagation of a crack from the desired break location across the diameter of the fiber. In accordance with a further embodiment, the elastomeric material is compressed by first applying radially directed compressive forces to a limited zone of the elastomeric material at the desired break location of the fiber, and the zone of application of the compressive forces is progressively increased in both axial directions from the location of the desired break location.
An apparatus in accordance with the invention comprises a body of elastomeric material having a fiber-receiving opening extending therethrough between its ends and having major surfaces which extend parallel to the fiber-receiving opening and between the ends. An actuator having force applying surfaces is provided for applying compressive forces to the major surfaces of the body of elastomeric material whereby, upon placement of the optical fiber in the fiber-receiving opening of the body of elastomeric material with the desired break location substantially mid-way between the ends thereof and upon the imposition of compressive forces to the major surfaces of the body of elastomeric material, the body of elastomeric material will be compressed onto the optical fiber and will be elongated, and the optical fiber will thereby be gripped in the body of elastomeric material, and the optical fiber will be placed in tension and a crack will travel across the fiber at the desired break location. The body of elastomeric material may comprise at least two blocks of elastomeric material in side-by-side juxtaposed relationship, the two blocks having opposed surfaces with the fiber-receiving opening being on the opposed surfaces. In accordance with a further embodiment, the force-applying surfaces of the actuator are shaped to impart a curvature to at least portions of the body of elastomeric material in the vicinity of the desired break location of a fiber held in the fiber receiving opening during the application of compressive forces to the major surfaces .